1. Field of the Invention
The present invention relates to a substrate processing unit and a processing method.
2. Description of the Related Art
In the photolithography in processes of semiconductor device fabrication, for example, resist coating treatment for applying a resist solution to the surface of a wafer to form a resist film, exposure processing for exposing a pattern on the wafer, developing treatment for developing the exposed wafer, and the like are performed to form a predetermined circuit pattern on the wafer.
At present, a spin coating method is in the mainstream as a method of applying the resist solution in the above-described resist coating treatment. According to the spin coating method, the resist solution is discharged to the center of the wafer and the wafer is rotated. This allows the resist solution applied on the wafer to spread by centrifugal force, whereby a uniform resist film can be formed over the entire face of the wafer. Thereafter, heating is performed in a heat treatment unit to dry a solvent in the applied resist solution.
However, in the spin coating method, the wafer is rotated at high speed, whereby a large amount of resist solution scatters from the peripheral portion of the wafer, which results in a big waste of resist solution. Moreover, the unit is contaminated by the scatter of the resist solution, thereby causing harmful effects such as necessity for frequent cleaning.
Therefore, instead of the spin coating method in which the wafer is rotated, a method, in which a nozzle for discharging the resist solution and the wafer are moved relative to each other to apply the resist solution having low viscosity, for example, evenly on the wafer in lattice form, is conceivable.
However, also in such method of applying the resist solution in the manner of the so-called single stroke, there is a fear that a resist film is not uniformly formed since the resist solution applied at the peripheral portion of the wafer protrudes by surface tension. Even if exposure is performed with the resist film protruding at the peripheral portion, the peripheral portion becomes a defective portion which can not be used as a product, thereby decreasing yields correspondingly.
On the other hand, it is considered that the resist solution having relatively low viscosity is suitable in the case of the method in which the resist solution is applied in the manner of the so-called single stroke, whereby there is a fear that evaporation rate becomes too high to form unevenness on the resist film if heating at high temperature is performed after coating as in the conventional method.
Therefore, although it is considered to be preferable that the solvent in the resist solution is slowly dried by reducing a pressure inside the unit to dry it after the resist solution is applied on the wafer, thereafter it is necessary to pay attention to uniformity of air current on a surface portion of the wafer and the above-described protruding portion of the resist solution at the peripheral portion of the wafer.
The present invention is made in view of the aforesaid points and its object is to make a film thickness of a coating solution such as the resist solution uniform by, for example, controlling the generated air current to remove protuberance formed at the outer peripheral portion of a substrate by surface tension when processing such as drying the solvent in the resist solution after application of the resist solution is performed.
According to a first aspect of the present invention, a substrate processing unit for performing predetermined processing on a substrate in a processing section after applying a coating solution to the substrate comprises exhaust means for reducing a pressure inside the unit, and a current plate for rectifying air current generated in the processing section due to exhaust by the exhaust means, which is arranged above the substrate, an underneath surface of the current plate having a protrusion which protrudes downward compared with other portions thereof corresponding to an outer peripheral portion of the substrate.
According to a second aspect of the present invention, a substrate processing unit for performing predetermined processing on a substrate in a processing section after applying a coating solution to the substrate comprises exhaust means for reducing a pressure inside the unit, and a current plate for rectifying air current generated in the processing section due to exhaust by the exhaust means, which is arranged above the substrate, an underneath surface of the current plate being flat and besides a distance between the underneath surface thereof and a treated surface of the substrate being 0.5 mm to 2.0 mm.
According to a third aspect of the present invention, a substrate processing unit for performing predetermined processing on a substrate in a processing section after applying a coating solution to the substrate comprises exhaust means for reducing a pressure inside the unit, and a current plate for rectifying air current generated in the processing section due to exhaust by the exhaust means, which is arranged above the substrate, an underneath surface of the current plate being flat and besides surface roughness of the underneath surface thereof being 0.2 xcexcm or less.
According to a fourth aspect of the present invention, a substrate processing unit for performing predetermined processing on a substrate in a processing section after applying a coating solution to the substrate comprises exhaust means for reducing a pressure inside the unit, a current plate for rectifying air current generated in the processing section due to exhaust by the exhaust means, which is arranged above the substrate, and a heating device for heating a peripheral portion of the current plate.
According to a fifth aspect of the present invention, a substrate processing unit for performing predetermined processing on a substrate in a processing section after applying a coating solution to the substrate comprises exhaust means for reducing a pressure inside the unit, and a current plate for rectifying air current generated in the processing section due to exhaust by the exhaust means, which is arranged above the substrate, a peripheral portion of an underneath surface of the current plate having a color which is lower in lightness than that of other portions thereof.
According to a sixth aspect of the present invention, a substrate processing method of performing predetermined processing on a substrate in a processing section after applying a coating solution to the substrate comprises the steps of reducing a pressure inside the processing section, measuring the pressure inside the processing section by pressure measuring means, and performing drying processing of the coating solution on the substrate by changing pressure reduction speed when the measured value of the pressure exceeds a predetermined value.
According to a seventh aspect of the present invention, a substrate processing method of performing predetermined processing on a substrate in a processing section after applying a coating solution to the substrate comprises the steps of reducing a pressure inside the processing section, measuring an amount of change in pressure inside the processing section, and performing drying processing of the coating solution on the substrate by changing pressure reduction speed when the amount of change in pressure exceeds a predetermined value.
According to an eighth aspect of the present invention, a substrate processing method of performing predetermined processing on a substrate in a processing section after applying a coating solution to the substrate comprises the steps of covering above of the substrate with a current plate of which underneath surface is flat, and reducing a pressure inside the processing section, wherein an area of a portion which is uniform in film thickness of a coating film by the coating solution on the substrate is controlled by adjusting a distance between the current plate and a top surface of the substrate.
According to the present invention, predetermined processing is performed under reduced pressure and, in particular, the present invention has a great effect on drying of the coating solution on the substrate. In addition, since the current plate for rectifying air current generated in the processing section is provided and the underneath surface of the current plate has a the protrusion which protrudes downward compared with the other portions thereof corresponding to the outer peripheral portion of the substrate, even if there is a protruding portion of the coating solution at the peripheral portion of the substrate, the protruding portion is made low by flow of the air current when a pressure is reduced, and consequently a coating solution film which is uniform as a whole is formed on the substrate.
According to the present invention, even if the underneath surface of the current plate is flat, a distance between the underneath surface thereof and the treated surface of the substrate is appropriately set, thereby improving the uniformity in film thickness of the solution film of the coating solution on the substrate.
According to the present invention, the underneath surface of the current plate is flat and besides the underneath surface thereof is set smooth, thereby preventing turbulence from occurring and improving the uniformity in film thickness of the solution film of the coating solution on the substrate.
According to the present invention, a heating device for heating a peripheral portion of the current plate is provided, thereby promoting vaporization of the solvent in the coating solution at the peripheral portion of the substrate and improving the uniformity in film thickness of the solution film of the coating solution.
According to the present invention, a peripheral portion of the underneath surface of the current plate has a color which is lower in lightness than that of other portions thereof, that is, a deep color, thereby promoting vaporization of the solvent in the coating solution at the peripheral portion of the substrate and improving the uniformity in film thickness of the solution film of the coating solution.
According to the present invention, drying processing of the coating solution on the substrate can be performed under appropriate reduced pressure by changing pressure reduction speed, which is effective in promoting drying.
According to the present invention, it is possible to control an area of a portion which is uniform in film thickness of the coating film by the coating solution on the substrate by adjusting the distance between the current plate and the top surface of the substrate.